About organic implementation of new stuff (fingers crossed)
Just rewatching the multiplayer session stream. Iirc it wasn't mentioned how you would you would fit additional gimmicks like power-ups into the game: Maybe it's viable to stretch the idea of the bored greater spirit. In the "Gods must be hungry" universe, the duty at hand is celebrated by making a colourful event out of it. The tone in "Kiln" is a little different, but why not have the greater spirit comment how boring the battle is, and her spice it up a bit, etc.?
Balancing and power-ups
Say the kiln health points are 90% for team A and 50% B. Greater spirit moans how one-sided this is and, in order to adjust the balance, drops a bunch of ready-made pots or power-ups for (currently) losing team B. As soon as the difference in health points have shrunk, she leaves another remark and stops the support.
Such actions could also help fight back spawnkilling ( I dunno whether this is or will be an issue).
Although it seems it was the time restrictions that kept the voice-acting at the essential minimum, the voiceless-ness of the grumpy flying buttballs is what makes them cute to me. If the aim was to keep their characteristics in a future full game version, a player's cry for help could also be uttered by a nonchalant remark of the greater spirit.
Example: A player of the green team wishes for support in battle, and thus hits the according key/button.
Greater one: "Ha, looks like that fat lil' fella could use some help." (maybe with a hint of the location, like "at the fountain" or "on the cliff"
In case the developers would like to be the team size not bigger than a dozen, this hint would be sufficient enough since
a) Kiln is no Quake, so the gameplay speed and clear map design allows for a HUD-less manual looking for the mate in trouble
b) in such smaller teams like imagined above, it is very likely each player takes his distinct role for his team: You won't have to check for 4 mates of the same visual characteristics simply because there aren't that many.
c) this would even add an element of thrill to it since it is a general cry for attention - 'general' meaning 'percetable for both teams'. As a result, both teams are likely to react and so the dynamic of the wole battle is affected. While this whole idea may be too krass, it would definitely suit the character of the greater spirit.
TL;DR All ideas about power-ups and communication could be implemented believably via the greater spirit.
PS: Please help me improve my comma game since I am no native English speaker.